Siemens SIMATIC S7-1200 System Manual page 1117

Hide thumbs Also See for SIMATIC S7-1200:

Table of Contents

Parameter and type

Consider the following received hexadecimal coded message: "68 10 aa 68 bb 10 aa 16"

and the configured start sequences shown in the table below. Start sequences begin to be

evaluated when the first 68H character is successfully received. Upon successfully receiving

the fourth character (the second 68H), then start condition 1 is satisfied. Once the start

conditions are satisfied, the evaluation of the end conditions begins.

The start sequence processing can be terminated due to various parity, framing, or inter-

character timing errors. These errors result in no received message, because the start

condition was not satisfied.

Table 13- 16 Start conditions

Start condition

First Character

End conditions for the Receive_P2P instruction

The end of a message is determined by the specification of end conditions. The end of a

message is determined by the first occurrence of one or more configured end conditions.

The section "Message end conditions" in the topic "Configuring receive parameters

(Page 1097)" describes the end conditions that you can configure in the Receive_Config

instruction.

You can configure the end conditions in either the properties of the communication interface

in the device configuration, or from the Receive_Config instruction. Whenever the CPU

transitions from STOP to RUN, the receive parameters (both start and end conditions) return

to the device configuration settings. If the STEP 7 user program executes Receive_Config,

then the settings are changed to the Receive_Config conditions.

S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK

First Character +1

Communication processor and Modbus TCP

Sequence 4 ignore/compare control for each character. Default val-

Sequence 4 start characters (5 characters), Default value: 0

First Character +2

13.3 Point-to-point (PtP) communication

First Character +3

First Character +4